The Planck constant

THE PLANCK CONSTANT

Black body is a full radiator, that means a body that absorb all colliding rays. Such body is also the best rays emitter of all other bodies of the same temperature. In the 19th century scientists researched radiation of different bodies. They found the interdependence between the emissivity, the wavelength and the body's (emitter's) temperature (see the picture).

The spectral decomposition of the black body radiation

The shape of the curve is temperature dependent. For higher temperatures the curve achieves higher values and its maximum shifts to the waves of the smaller length. The dependence between the body's temperature (T) and the wave's length ( lambda

_max) achieving which the function reaches its maximum is given by the formula:

(1)

where C = 2,898*10^-3m*K

And so

_max is directly proportional to the inverse of the temperature. That relationship can be easily imagined by the example of heating a metal rod. In the heating beginning the maximum will be at the invisible infra-red waves. After while the maximum will be at the red waves - the rod will glow red. Heating the rod some more the maximum shifts to the waves of the smaller length. Finally the rod becomes white because of emitting the infra - red waves and the whole range of the visible radiation.
The curve describing the emission of the black body was achieved experimentally. The phenomenon can't have been explained using the Maxwell laws nor any classic physical ones.
In 1900 Max Planck formulated a new theory of radiation. He suggested the idea of atoms and other particles emitting radiation not perpetual but in the form of energy portions depended only on the wave frequency (v). That dependence is given by the formula below:

(2)

where h - the Planck constant equal 6,6*10^-34 J*s

The single portion ef energy was called the quantum. The theory described the experimentally achieved curve well. The h quantity become the basic one for quantum physics.

QUANTYM THEORY - THE NEW GREAT IDEA